The present invention relates to a magnetic tape cassette including tape reels on which a magnetic tape is wound and, more particularly, to a holding structure of a magnetic tape which is suitable for reducing the size and improved reliability.
Conventionally, as disclosed in, for example, Japanese Patent Unexamined Publication No. 60-154375, in order to reduce the size of a magnetic tape cassette, flanges of tape reels are eliminated, and a supply reel and a take-up reel are located in such a manner that their maximum winding diameters overlap each other, thereby decreasing a pitch between the reels. Thus, it is possible to decrease the plane area and the height of the magnetic tape cassette. In this type of cassette, sheet-like members are inserted between a casing and the magnetic tape so as to prevent side edge misalignment of the magnetic tape which is caused by absence of flanges.
A tape cassette wherein no flanges are formed on tape reels involves problems in relation to side edge alignment of a magnetic tape. That is to say, levels of side edges of the magnetic tape wound on the reel become irregular, and levels of side edges of the magnetic tape with respect to a tape moving system of the apparatus are not constant. In order to solve these problems, the above-mentioned method of inserting sheet-like members is employed; however, the sheet-like members and the magnetic tape always slide on each other so that edges of the magnetic tape are likely to be damaged. Moreover, the sheet-like members are located in such a manner that gaps of predetermined distances are defined between the sheet-like members and the casing of the tape cassette, and, consequently, levels of side edges of the magnetic tape with respect to the tape cassette can not be precisely determined. If a deviation is caused between the level of the magnetic tape and the level of the tape moving system of the apparatus, movement of the magnetic tape becomes unstable, so that reliable track tracing can not be conducted, and that the tape will be easily damaged by flanges of tape guides or the like, thereby deteriorating the quality of reproduced images.